Apparatus for controlling highway crossing signals



July 20, 1954 H. A. HAINES 2,684,435

APPARATUS FOR CONTROLLING HIGHWAY CROSSING SIGNALS Filed Jan. 26, 1952XTH ull

Q in N 1 L m E w l l I E v QT Q n\ N a? ,g e: 1% R s V k M =INVENTOR.Harvey A. flames. a if BY N U). L. 11$

HIS 4TTOHNEV Patented July 20, 1954 UNITED STATE Westinghouse Air BrakeCompany; Wilmerding, Pa, a corporation of Pennsylvania ApplicationJanuary 26, 1952*, Serial No. 268,395

rem oFFICE 8 Claims. 1

My invention relates to apparatus for controlling highway crossingsignals, and particularly to apparatus for protecting against momentarylosses of track circuit shunt in highway crossing signal control systemswhich 64 body a capacitor for delaying the starting of the operation ofthe highway crossing signal after a train approaches' within a givendistance of the intersection of a highway with a railway track.

It is important that a highway crossingsignal be operated long enoughbefore the arrival of atrain at an intersection of a highway with arailway track, to provide ample warning to users of the highway that atrain is approaching, so that users of the highway will have sufiicienttime to get into the clear. It is, however, des'ir'ablethat a highwaycrossing signal be not operated so long before the arrival of a train atthe intersection as to unduly delay users of the highway and therebycause them to become careless about obeying indications given by highwaycrossing signals.

It iswell-known practice to install insulated joints for" dividing arailway track into approach and crossing track sections adjacent theintersection of a highway with the railway track, for starting theoperation of a highway crossing signal in response tothe arrival of atrain witha given distance from the highway crossing, and for continuingoperation of the highway crossing signal while the train is moving overthe crossing. If train movements are in both directions over the track,an approach section is providedin each direction from the intersection.Operation of a: highway crossing signal is started-5 when a trainapproaching the intersection enters the corresponding approach section,and is continued until the train vacates the crossing track section.

From the standpoint of maintenance costs of insulated joints, as well asof the original cost of installingthem", it is desirable to keep fromdividing a railway track into any more sections than can be" avoided;If, for some other purpose;- such, for exam le, as the control of arailway signal, insulated joints are already installed in a railwaytrack in the vicinity of an intersection of a highwaywith therailwaytrack, biit'a-t a location which isfarthe'r from the intersection orcrossing than isinecessafry for providing ample warning to users of thehighway when a" is'approaching' the crossing, acapacitor resistorarrangement can be used" for delaying starting of the operation of ahighway crossing signal for a desired period of time after 2 the leadingend of a train approaching the intersection has passed over thoseinsulated joints.

It has been found; however, that in a highway crossing signal controlsystem in which a capacito'r-resistor arrangement is employed for delaying the starting of operation of a highway cro sssig'nal when a trainenters approach control track section, there may be a dangerouscondition if there should be a momentary loss of track circuit shunt ofthe approach track section. This is because the capacitor, in thecapacitor-resistor arrangement, may become recharged because of amomentary loss of track circuit shunt, and delay still further thestarting of the operation of the highway crossing signal. If themomentary loss of shunt of the track circuit for an approach tracksection should. "ccur near the end of the delay period normally providedby the capacitor-resistor arrangement, the resulting delay period mightbe almost double the normal delay period intended, so that the highwaycrossing signal would provide very little, if any, warning of theapproach of a train before the train arrived on the crossing tracksection.

An object of my invention is therefore the provision of means forprotecting against a momentary loss of shunt of a track circuit for anapproach control section in a highway signal control system in which acapacitor-resistor arrangement is used for delaying the starting ofoperation of the highway crossing signal after a train enters theapproach control section. v

A feature of my invention, for accomplishing this object, is theprovision of time element means for effecting energization of a controlstick relay only upon the lapse of a measured period of time if thetrack relay for an approach control section becomes energized because ofa momentary loss of track circuit shunt while a train is on the approachcontrol section, or because thetrain has left the approach controlsection, and for effecting the charging of a capacitor only upon thelapse of a further measured period of time after the control stick relayhas become energized.

Another feature of my invention, in an ar rangement for protectingagainst a momentary loss of track circuit shunt otan approachcontroltrack section in a highway crossing signal control system, is theprovision of means for discontinuing operation of the highway crossingsig rial as soon as a train Va'cates the crossing track section; g z p UI shalldescribe one form of apparatuse'mbodying my invention, and shallthen point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic View showing one form ofapparatus embodying my invention, in which a railway track which isintersected by a highway is divided to form a crossing section at thehighway and an approach control section adjacent one end of the crossingsection; in which an approach stick relay, designated by the referencecharacter ASE, may become operated immediately in the event of a momntary loss of track circuit shunt of an approach control section whichoccupied by a train, or when the train vacates the ap proach controlsection; in which a time element device, designated by the referencecharacter efiects energization of a control stick relay, designated bythe reference character TEPS, upon the lapse of a measured period oftime after relay ASE becomes operated; and in which the time elementdevice TE then effects charging of an energy storing device such, forexample, as a capacitor, designated by the reference character I, onlyupon the lapse of a further measured period of time after relay TEPS hasbecome energized.

Similar reference characters refer to similar parts in the drawing.

Referring further to the drawing, a stretch of railway track is shownintersected by a highway designated by the reference character H. Ahighway crossing signal, designated by the reference character XS, whichmay be of any suitable design, but which, as shown in the drawin is ofthe dashing light type, is located adjacent the intersection of thehighway H with the rail way track. I shall assume that train movementsover the stretch of track from left to right, as shown in the drawing,are in the eastbound direction, and therefore traffic movements fromright to left, as shown in the drawing, are in the westbound direction.

The rails or the railway tra are divided by insulated joints 3 to form acrossing section, designate by the reference character XT, at theintersection of the highway with the railway track, and an eastboundapproach control track section, designated by the reference characterl1, adjacent the west end of section XT.

Each of the track sections and Vi is provided with a track circuit whichincludes a relay YEP-c or lTR, respectively, connected across the railsadjacent one end of the section, and a suitable source of current, suchas a battery 5, connected across t e rails adjacent the opposite end ofthe section.

The approach stick relay ASR has a pickup and a stick circuit, both ofwhich are controlled by a front contact or" the approach section trackrelay lTR, and the pickup circuit is also controll d by a back Contact lof a repeater relay, designated by the reference character TEPP, for thecontrol stic.: relay TEPS.

Time element device TE may be of the thermal type, provided with acontrol element, designated by the reference character 9, and having aslow pickup front contact H which becomes closed when the controlelement 9 has been energized for a measured period of time, and alsohaving a slow closing back contact l2 which becomes closed upon thelapse of a further measured period of time after the control element 5has become deenergized. An energizing circuit for time element device TEis at times completed through a 4 front contact 8 of relay ASR and theback point of a contact ll! of relay TEPS.

Both a pickup and a stick circuit for relay TEPS are controlled bycontact 3 of relay ASR. The pickup circuit for relay TEPS also includescontact ll of time element device and the stick circuit includes controlelement 9 of time element device TE.

The capacitor t is in series with a resistor, designated by thereference character 7', and with the baclt contact ii of time elementdevice TE, in a circuit path which is in multiple with the winding ofrelay TE'PS in the stick circuit for this relay. Relay TEPS is renderedslow releasing by capacitor t and resistor r in this path in multiplewith its control winding when relay ASE becomes deenergized and itscontact 8 becomes opened.

A crossing signal control relay, designated by the reference characterXR, is controlled by front contacts of relays TEPP, ASR and XTR, and mayalso be controlled by contacts of directional stick relays which are nota part of my invention and are therefore not shown in the drawing. RelayX5, is normally energized.

A flasher control relay, designated by the reference character FR, iscontrolled by a back contact ll of relay XR, and is therefore normallydeenergized. Relay FR is of a Well-known type having a movable contactelement [9 which, while relay FR is energized, oscillates between afirst position in which it engages a first fixed contact element a and asecond position in which it engages a second fixed contact element 1;.

A shown in the drawing, highway crossing signal XS embodies two lamps,designated by the reference characters is and 2c, the lighting circuitsfor which include contacts iii-b and lS-a, respectively, of relay FE,and a back contact E8 of relay X t. Lamps is and 2e are thereforenormally not lighted. When relay XR becomes deenergized, causing itscontact H to become closed in the circuit for energizing relay FR, andcausing its contact 58 to become closed in the lighting circuits forsignal XS, lamps le and 2c of signal XS will display a flashingindication on account of being repeatedly lighted alternately throughthe contacts ill-b and iii-a of relay FR.

The control and lighting circuits shown in the drawing may be suppliedwith energy from any suitable source such, for example, as a batter,designated by the reference character Q, having terminals B and N.

Having described, in general, the arrangement and control of theapparatus shown by the accompanying drawing, I shall now describe, indetail, its operation.

As shown in the drawing, all parts of the apparatus are in their normalcondition, that is, each of the track sections is unoccupied, andtherefore the track relays XTR and ITR are energized; relays TEPS, TEPP,ASE, and KR are energized; capacitor 75 is in the charged condition;control element 9 of time element TE is in series with the winding ofrelay TEPS, in the stick circuit for relay TEPS, and is thereforeenergized insufficiently for closing contact ii of time element deviceTE or for retaining this contact closed; and relay FR and crossingsignal XS are deenergized.

Relay ASR is energized by its stick circuit passing from terminal B,through contact 5 of relay l'I'R, contact 6 of relay ASR, and thewinding of relay ASR to terminal N. Relay TEPS is also energized by astick circuit, passing from terminal B, through contact. 8 of relay ASR,control element 9 of time element device TE, front point of contact toof relay TEPS, and the Winding of relay TEPS to terminal N.

Control element 9 of time element device TE, on account of beingincluded in. series with the winding. of relay is not receivingsuliicient energy for closing. its front contact I l, and thereforecontact H is open, and its back contact 1.2 is closed. The chargingcircuit is completed for capacitor 25, and is the same as the stickcircuit traced. for relay TEPS' as far as the front point of contact toof relay TEPS, and then passes through contact 12 of time element deviceTE, resistor r, and capacitor t to terminal N. Control element. t oftime element device TE is therefore also in series with resistor r andcapacitor 1. and this too prevents control element 9 of time elementdevice TE from receiving sufiicient energy to" close its front contact Hand open its back contact l2.

Relay TEPP is energized by an obvious circuit which includes contact I3of relay TEPS.

Relay XRZ is energized by a. circuit passing from terminal B, throughcontact It of relay TEPP in multiple with contact l5 of relay ASR,contact it of relay XTR, and the winding of relay XRv to terminal N.

I shall assume that, with. apparatus embodying my invention as shown inthe accompanying drawing, an eastbound train enters section IT,deenergizing relay ITR. On account of relay lT-R being deenergized, itscontact 5 will open the stick circuit traced for relay ASR, causingrelay ASH to become deenergized. The stick circuit traced for relay TEPSand: the charging circuit for capacitor t will then be opened atcontact8 of relay ASR. Current will now be discharged from capacitor t, throughresistor r, contact 52 of time element device TE, and the 'Winding ofrelay TEPS back to capacitor t. Relay TEPS will be rendered slowreleasing by the energy thus dissipated from capacitor 2?. Contact iiiof relay TEPS will therefore be retained closed for a brief period oftime, so that. relay TEPP will remain energized for a brief period oftime. Although contact it of relay ASR opens, in the control circuittraced for relay XR, relay XR is retained energized for a period of timeby current passing through. contact I i of relay TEPP.

By the timethat contact i3 of relay TEPS has been released, and in turncontact It of relay TEPP has opened and caused relay XR. to bedeenergized, the eastbound train will have arrived at a locationdesignated on the drawing as the starting point. The location of thisstarting point willof course be diiierent for difierent trains,depending on their speed, so that, the higher the speed of the train,the farther the starting point will be from the entering end of sectionVI, and the nearer it will be to the crossing. The parts ithe apparatusare so proportioned that, for trains traveling at the highest speed, thestarting point will be far enough from the intersection to provide amplewarning to users of the highway.

When relay XR becomes deenergized, relay FR will become energized by itscircuit passing from terminal B, through contact ll of relay XR, and thewinding of relay FR. to terminal N. Relay FR, upon thus becomingenergized, will oscillate its movable contact element 19' to repeatedlyengage the fixecl contact elements a and b alternately. Lamp 2e willtherefore be lighted by a circuit passing from terminal B, throughcontact I'8' of. relay XR', contact Iii-a of relay FR, and

6 lamp 2c to terminal N. When the movable contact element [9 engagesfixed element b, lamp l e will be lighted by its circuit passing fromterminal B, through contact is of relay XR, contact 19-17 of relay FR,and lamp 1 e to terminal N.

When the train enters section XT, deenergizing relay XTR, contact I6 ofrelay XTR will open the circuit for relay XR, at another point.

When the train leaves section IT, relay ASR will become energized by itspickup circuit passing from terminal B, through contact 5 of relay ITR,contact 5 of relay TEPP, and the winding of relay A83. to terminal N.Relay ASR, upon thus becoming energized, will complete its stick circuitpreviously traced. With relay ASE energized, its contact IE will beclosed in the circuit previously traced for relay XR, which circuit willhowever still be open at contact I t of relay m, and therefore relay XRwill remain deenergized.

Contact 3 of relay AER, upon becoming closed, completes an energizingcircuit for time element device TE, this circuit passing. from terminalB, contact 8 of relay ASR, control element a of time element device IE,and the back point of contact if? of. relay TEPS to terminal N.

Upon the lapse of a measured period of time determined by time elementdevice TE, front contact l l or" time element device TE will becomeclosed, thereby completing a pickup circuit for relay TEPS, this circuitpassing from terminal 5, through contact 8 of relay ASH, contact I l oftime element device and. the winding of relay TEPS to terminal N. RelayTEPS, upon thus becoming energized, will complete its stick circuitpreviously traced.

With control. element ll of. time element device TE in series with thewinding of relay TEPS, the energization of control element 9 will bereduced to such an extent that contact ii of time element device TE willopen, and, upon the lapse of a further measured period of time, contact12 or time element device TE, will become closed. When contact ll oftime element device TE becomes closed, the charging circuit will becompleted for capacitor t, as previously described.

with contact 53 of relay TEPS now closed, relay TEPP will again becomeenergized by its circuit previously described. Contact M ofrelayTEPP'wiil therefore again be closed. With contact l of relay now open,the pickup circuit traced for relay ASE will be open, but relay ASR.will remain energized by its stick circuit previously traced.

On account of relay .ASR' having been energized as soon as the trainleft section IT, a circuit Will be completed for energizing relay XR assoon as the train leaves section XT, permitting relay XTR. to close itscontact t6. Relay XE will therefore open its contacts El and 18,deenergizing relay FR and. signal XS as soon as the train has vacatedsection XT. All parts of the apparatus shown in the accompanying drawingwill therefore again be the normal condition.

I shall now assume that, with all parts of the apparatus-shown in theaccompanying drawing, again in their normal condition, an eastboundtrain enters section ET, deenergizing relay I TR, which in turn causesrelays ASE and TEPS to be deenergized, as previously described. I shallassume further that a momentary loss of. track circuit shunt or"-section iT occurs before relay TEPS has released its front contacts.Relay TEPP will therefore stillbe energized, and its contact 7 will beopen, so that the pickup circuit for relay ASH will not become closedfor energizing relay ASR i When relay TEPS releases its front contactsat the end of the slow release period provided by the discharge ofenergy from capacitor t, as previously described, relay TEPP will becomedeenergized and the pickup circuit previously traced for relay ASE, willbe completed.

As soon, however, as the momentary loss of shunt ends, contact 5 ofrelay i'IR will again become opened, causing relay ASE to again bedeenergized. It follows that, after contact I i of relay 'IEPP becomesopened at the end of the release period of relay TEPS, contact it ofrelay ASR can be closed for only a very brief period of the momentaryloss of shunt remaining, and that therefore the highway crossing signalXS can be operated, at the most, for only the duration of the momentaryloss of shunt.

I shall next assume that all parts of the appa ratus shown in theaccompanying drawing are again returned to the normal condition, andthat relay ASE. becomes deenergized by an eastbound train enteringsection lT, causing relay TEPS and, in turn, upon the lapse of a delayperiod, relay 'IEPP also to become deenergized, so that relay XR isdeenergized and the operation of signal XS is started. I shall assumefurther that a momentary loss of shunt then occurs, so that contact 5 ofrelay iTR completes the pi kup circuit for relay ASR. Rela ASE, uponclosing its contact l5, closes a circuit for energizing relay 2B whichthen interrupts peration of signal XS. With relay ASR energized, theenergizing circuit for control element e of time element device IE willbe completed, as previously traced, but before time element device TEcan close its contact l l for completing a pickup circuit for relayTEPS, the loss of shunt will be ended. With relay iTP, againdeenergized, relay ASH will in turn also become deenergized, and itscontact it: will open the circuit for relay XR, so that the operation ofsignal XS will be resumed.

From the foregoing description of the operation of apparatus embodyingmy invention, as shown in the accompanying drawing, it is clear that,with my invention, if a loss of track circuit shunt occurs at any timewhile a train is on section l'I, relay TEPS cannot become energizeduntil the lapse of a measured period of time required for closingcontact 1 l of time element device '.E. The period of time required fordevice TE to close its front contact i l is longer than the duration ofmomentary loss of track circuit shunt that might be expected, andtherefore relay TEPS will not close its ront contacts because of anysuch momentar loss of shunt. The capacitor 1 cannot become charged untilthe lapse of a still further measured period of time determined by thetime required for time element device IE to close its back contact l2.

It follows, therefore, that, with apparatus embodying my invention, theonly interruption to the operation of signal XS that can occur due to amomentary loss or" track circuit shunt of section II will be for thebrief period of the momentary loss of track circuit shunt, and thisperiod of interruption of the operation of signal XS cannot be extendedby the delay means comprising capacitor 25 and resistor r for normallydelaying the starting of the operation of signal XS when a train enterssection lT.

Although I have herein shown and described only one form of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a control system for a highway crossing signal adjacent theintersection of a highway with a railway track which is divided to forma crossing section including the intersection and an approach controlsection adjacent one end of said crossing section, each of said sectionsbeing provided with a track circuit including a source of current and atrack relay which is normally energized but which becomes deenergized inresponse to occupancy of the corresponding section by a train, thecombination embodying means for protecting against momentary losses ofshunt of an approach control section comprising, an approach stickrelay, a time element device having a control element and having a backcontact which becomes opened and also a front contact which becomesclosed when said control element has been energized a given measuredperiod of time by current of suitable magnitude, said front contactagain becoming opened and said back contact again becoming closed whenthe energize,- tion of said control element has been reduced andmaintained below a given level for a second measured period of time, anenergy storing device, a control stick relay, a repeater relaycontrolled by a front contact of said control stick relay, a pickup anda stick circuit for said approach stick relay each controlled by a frontcontact of the track relay for said approach control section and saidpickup circuit also controlled by a back contact of said repeater relay,means controlled by a front contact of said approach stick relay and bya back contact of said control stick relay for energizing the controlelement of said time element device, a pickup and a stick circuit forsaid control stick relay each controlled by a front contact of saidapproach stick relay and said pickup circuit also controlled by saidfront contact of said time element device and said stick circuitincluding said control element of said time clement device, a path inmultiple with the control winding of said control stick relay includingsaid energy storing device in series with said back contact of said timeelement devi e, and means controlled by a front contact of said repeaterrelay in multiple with a front contact of said approach stick relay bothin series with a front contact of the track relay for said crossingsection for controlling said highway crossing signal.

2. In a control system for a highway crossing signal adjacent theintersection of a highway with a railway track which is divided to forma crossing section including the intersection and an approach controlsection adjacent one end of said crossing section, each of said sectionsbeing provided with a track circuit including a source of current and atrack relay which is normally energized but which becomes deenergized inresponse to occupancy of the corresponding section by a train, thecombination embodying means for protecting against momentary losses ofshunt of an approach control section comprising, an approach stickrelay, a time element device having a control element and having a backcontact which becomes opened and also a front contact which becomesclosed when said control element has been energized a given measuredperiod of time by current of suitable magnitude, said front contactagain becoming opened and said back contact again becoming closed whenthe energization of said control element has been reduced and maintainedbelow a given level for a second measured period of time, an energystoring device, a control stick relay, a pickup and a stick circuit forsaid approach stick relay each controlled by a front contact of thetrack relay for said approach control section and said pickup circuitalso controlled by a contact which becomes closed in response todeenergization of said control stick relay, means controlled by a frontcontact of said approach stick relay and by a back contact of saidcontrol stick relay for energizing the con trol element of said timeelement device, a pickup and a stick circuit for said control stickrelay each controlled by a front contact of said ap proach stick relayand said pickup circuit also controlled by the front contact of saidtime element device, said energy storing device included in series withsaid back contact of said time element device in a path in multiple withthe control winding of said control stick relay, and means controlled bya front contact of said control stick relay in mult ple with a frontcontact of said approach sticl: relay and including a front contact ofthe track relay for said crossing section for controlling said highwaycrossing signal.

3. In a control system for a highway crossing signal adjacent theintersection of a highway with a railway track which is divided to forma crossing section including the intersection and an approach controlsection adjacent one end of said crossing section, each of said sectionsbeing provided with a track circuit including a source of current and atrack relay which is normally energized but which becomes deenergized inresponse to occupancy of the corresponding section by a train, thecombination embodying means for protecting against momentary losses ofshunt of an approach control section comprising, an ap-= proach stickrelay, a control stick relay, a slow pickup and; slow release timeelement device having a front contact which closes upon the lapse of ameasured period of time after said time element device becomes energizedand having a back contact which closes upon the lapse of a econdmeasured period of time after energy is removed from said time elementdevice, an energizing circuit for said time element device controlled bya front contact of said approach stick relay and by a back contact ofsaid control stick relay, a pickup and a stick circuit for said controlstick relay each controlled by a front contact of said approach stickrelay and said pickup circuit also controlled by the front contact ofsaid time element device, an energy storing device, a path includingsaid energy storing device in series with the back contact of said timeelement device connected across the control winding of said controlstick relay, a pickup and a stick circuit for said approach stick relayeach controlled by a front contact of the track relay for said approachcontrol section and said pickup circuit also controlled by a contactwhich becomes closed in response to deenergization of said control stickrelay, and means controlled by a front contact of said control stickrelay in multiple with a front contact of said approach stick relay andin series with a front contact of the track relay for said crossingsection for controlling said highway crossing signal.

4. In a control. system for a highway crossing signal adjacent theintersection of a highway with a railway track which is divided to forman approach control section adjacent said intersection, said approachcontrol section being provided with a track circuit including a sourceof current and a track relay which is normally energized but becomesdeenergized in response to occupancy of said approach section by atrain, the combination embodying means for protecting against momentarylosses of shunt of an approach control section comprising, an approachstick relay, a control stick relay, .a slow pickup and slow release timeelement device having a front contact which becomes closed upon thelapse of a measured period of time after said time element devicebecomes energized and having a back contact which becomes closed uponthe lapse of a second measured period of time after energy is removedfrom said time element device, means controlled by a front contact ofsaid approach stick relay and by a back contact of said control stickrelay for energizing said time element device, a pickup and a stickcircuit for said contro relay each controlled by a front contact of saidapproach stick relay and said pickup circuit also controlled by saidfront contact of said time clement device, an energy storing device, acircuit path including said enrgy storing device and said back contactof said time element device connected across the inding of said controlstick relay, pickup and a stick circuit for said approach stick relayeach controlled by a front contact of the track relay for said approachsection and the pickup circuit also controlled by a contact whichbecomes closed when said control stick relay becomes deenergized, andmeans including a. front contact controlled by said control stick relayin multiple with a front contact of said approach stick relay forontrolling said highway crossing signal.

5. In a control system for a highway crossing signal. adjacent theintersection of a highway with a railway track which is divided to forman approach control section adjacent said intersection, said approachcontrol section being provided with a track circuit including a sourceof current and a track relay which is normally energized but becomescleenergized in response to occupancy of said approach section by atrain, the combination embodying means for protecting against momentarylosses of shunt of an approach control section comprising, a controlstick relay, time element means, means controlled by a back contact ofsaid control stick relay and by a front contact of said track relay forenergizing said time element means, means controlled by said timeelement means for effecting energization of said control stick relay bya pickup circuit upon the lapse of a measured period of time after saidtrack relay becomes energized, a stick circuit for then retaining saidcontrol stick relay energized while said track relay remains energized,an energy storing device, means controlled by said time element meansand by said control stick relay for charging said energy storing deviceupon the lapse of a further period of time after said control stickrelay becomes energized, means including said energy storing device forrendering said control stick relay slow to release when said track relaybecomes deenergized, and means including a front contact controlled bysaid control stick relay for withholding operation of said highwaycrossing signal for a brief period of time after said track relaybecomes deenergized.

6. In a control system for a highway crossing signal adjacent theintersection of a highway with railway track which is divided to form anapproach control section adjacent said intersection, said approachcontrol section being provided a track circuit including a source ofcurrent and a track relay which is normally ener gized but becomesdeenergized in response to occupancy of said approach section by atrain, the combination embodying means for protecting against momentarylosses of shunt of an approach control section comprising, an approachstick relay, a control stick relay, time element means, a pickup and astick circuit for said approach stick relay each controlled by a frontcontact of said track relay and said pickup circuit also controlled by acontact which becomes closed in response to deenergization of saidcontrol stick relay, means controlled by a front contact of saidapproach stick relay and by a back contact of said control stick relayfor energizing said time element means, means controlled by said timeelement means for eiiecting energization of said control stick relay bya pickup circuit upon the lapse of a measured period or time after saidapproach stick relay becomes energized, a stick circuit controlled by afront contact of said approach stick relay for then retaining saidcontrol stick relay energized, an energy storing device, meanscontrolled by said time element device and by said control stick relayfor charging said energy storing device upon the lapse of a furtherperiod 01 time after said control stick relay becomes energized, meansincluding said energy storing device for rendering said control stickrelay slow to release when said approach stick relay becomesdeenergized, and means controlled by a front contact of said controlstick relay for withholding operation of said highway crossing signalfor a brief period of time after said approach stick relay becomesdeenergized.

7. In a control system for a highway crossing signal adjacent theintersection of a highway with a railway track which is divided to forman approach control section adjacent said intersection, said sectionbeing provided with a track circuit including a source of current and atrack relay which is normally energized but becomes deenergized inresponse to occupancy of said approach section by a train, thecombination embodying means for protecting against momentary losses ofshunt of an approach control section comprising, a control stick relay,time element means, means controlled by a back contact of said controlstick relay and by a front contact of said track relay for energizingsaid time element means, means controlled by said time element means foreffecting energization of said control stick relay by a pickup circuitupon the lapse of a measured period of time after said track relaybecomes energized, a stick circuit for then retaining said control stickrelay energized while said track relay remains energized, an

energy storing device, means controlled by said time element means andby said control stick relay for charging said energy storing device uponthe lapse of a further period of time after said control stick relaybecomes energized, a circuit path including said energy storing deviceconnected across the control winding of said control stick relay, andmeans controlled by a front contact of said control stick relay forwithholding operation or" said highway crossing signal for a period oftime after said track relay becomes deenergized.

8. In a control system for a highway crossing signal adjacent theintersection of a highway with a railway track which is divided to forman approach control section adjacent said intersection, said sectionbeing provided with a track circuit including source of current and atrack relay which is normally energized but becomes deenergized inresponse to occupancy of said approach section by a train, thecombination embodying means for protecting against momentary losses ofshunt of an approach control section comprising, a control stick relay,time element means, means controlled by said control stick relay and bysaid track relay for energizing said time element means when said trackrelay becomes energized, means controlled by said time eiement means forenergizing said control stick relay upon the lapse of a measured periodof time after said track relay becomes energized, stick circuit meanscontrolled by said track relay for then retaining said control stickrelay energized while said track relay remains energized, an energstoring device, means including a front contact of said control stickrelay for effecting charging of said energy storing device, meansembodying said energy storing device for rendering said control stickrelay slow to release when said track relay becomes deenergized, andcontrol means including a front contact of said control stick relay forwithholding operation of said highway crossing signal for a period oftime after said track relay becomes deenergized References Cited in thefile of this patent UNITED STATES PATENTS Number Name Date 1,934,094Saunders Nov. 7, 1933 2,097,827 Young Nov. 2, 1937 2,220,484 Jensen Nov.5, 1%0 2,379,209 Allen June 26, 1945 2,520,924 Blosser Apr. 1, 1952

